There are a boat load of tools for cross compiling between architectures on OpenBSD, but:

They are NOT maintained, except when needed by the developer(s) porting the OS to a new architecture.

They are NOT supported by the project for those outside the development team.

The developers will NOT answer questions about the tools, for reasons #1 and #2 above.

Anyone not a developer will not be able to help, due to #1, #2, and #3 above.

There have been presentations published at conferences that mention cross compiling efforts for new platforms. You should start your research with those. It is possible that if you posted a very polite query on misc@, a developer might give you some direction.

I need a good reference on the openbsd kernel and 'fopen_unlocked' system call as pertaining to the arm:xscale: pxa270 architecture.

It is probably safe to assume that the most polite answer you will be able to get from the developers is to read the kernel code and thinker with the it. If you are not able to read code itself and play with it I am afraid you will just get flamed.

I also want to reiterate the fact that unlike flakey cross compiling commonly used by NetBSDteam for example to produce kernel, userland, and packages for more exotic architectures in the OpenBSD world cross compiling is exclusively used to port the system to new architectures. All binaries on supported platforms are natively built including things like VAX, or Motorola 88 000 (I didn't make the mistake. I didn't mean to say 68 000, I meant to say 88 000). That is way they are so rock stable.

I downloaded and installed a gcc compiler to the phone itself via sdcard.
Now for the fun part: compiling the source directly on the machine.

I don't think that the machines have the exact same hardware.
Probably the next time Xanadux/familiar is run, the dmesg will be looked at.
Given that the zaurus and other ARM machines are supported, a dmesg should be easy to find. Devices in question can be multi-referenced between native, zaurus linux, and zaurus openbsd dmesgs.
On the other hand, I'm not sure which gcc release the compiler (pocketpc) is based upon.

Somewhat offtopic: I put Android on an sdcard to see if would work. Followed directions and it did. Shitty part is that there is no available root console, libraries, or any other thing necessary. Disappointing. Preference is to have a system with developer tools added.